1. Field of the Invention
The present invention relates to the use of a composition which contains 1-(2-ethylhexyl)glycerol ether for thermochemical disinfection.
2. Related Art
Mechanical disinfection methods are employed for disinfecting instruments especially in the clinical sector. In these, an aqueous composition is allowed to act, normally at elevated temperature, on the surface to be disinfected, cf. Anforderungen an die Hygiene bei der Aufbereitung bei Medizinprodukten, Bundesgesund-heitsblatt 44 (2001), 1115-1126.
Preparations currently employed in thermochemical disinfection methods can be roughly divided into three groups:
Compositions which Contain Short-Chain Organic Acids Such as Formic Acid, Acetic Acid or Citric Acid.
The effect of such monobasic or polybasic acids is disclosed inter alia in EP-A-0 505 763 and AT-A-382 310, see also Hygiene+Medizin 1989, 14, pages 69 et seq., GB-A-2 103 089 and Tierärztliche Umschau 1988, 43, pages 646 et seq. It is additionally proposed in DE-C2-42 00 066 to employ a 1.5% by weight aqueous solution of citric acid, optionally with the addition of malic acid or lactic acid, to inactivate hepatitis B viruses. However, a disadvantage which has emerged is that such disinfectants necessarily have a low pH and accordingly, especially when relatively high temperatures are used for disinfecting instruments, act as strong corrosives.
Compositions Which Contain Quaternary Ammonium Compounds.
These have proved, especially in disinfectants with a very high alcohol content, e.g. in anhydrous isopropanol/n-propanol or 80% strength ethanol, to be effective hand disinfectants (see, inter alia, WallhäuBer, Praxis der Sterilisation, Henkel Chemische Bibliothek, 4th edition, 1988, pages 75 et seq.). Disinfectants with a high alcohol content are, however, unsuitable for disinfecting instruments because they attack synthetic materials. In addition, disinfectants containing quaternary ammonium compounds are highly foaming, which restricts their use, especially for disinfecting instruments.
Compositions Which Contain Aldehydes Such as Formaldehyde, Acetaldehyde and Glutaraldehyde.
Aldehyde-containing disinfectants have been unwanted for some years because of the harmful effects on human health, especially of formalin, and because of their unpleasant odour.
Many materials (e.g. metal) of the surfaces of instruments (e.g. endoscopes) are moreover resistant to the agents used in known compositions for thermochemical disinfection for only a limited time and in a limited temperature range. Thus, known solutions used for thermochemical disinfection lead, at the temperatures necessary for use, to corrosion of the surfaces of treated articles, e.g. to rusting of metal, to hazing of glass, plastic or ceramics or to brittle synthetic materials. Replacement of the agents, lowering the concentration used and/or lowering the disinfection temperature are, however, subject to restrictions because the surface must be dependably cleaned and reliably disinfected and moreover a large number of microorganisms must be eliminated.
The disinfectant solutions conventionally employed, and corresponding concentrates, have disadvantages, however:                1. Many known agents are costly, leading to the respective disinfection method being uneconomic, especially if it is necessary to use high concentrations.        2. The known solutions for use must (i) contain comparatively high concentrations of agents, (ii) be employed at comparatively high temperatures and (iii) for a comparatively long time for dependable elimination of all relevant microorganisms. These three parameters are not unrestrictedly consistent with material-conserving disinfection and may lead to stress for the staff and/or environment from the solutions used.        3. Disinfectant concentrates are often not stable at low temperatures or on storage and are prone to discoloration and to foaming of the solutions prepared for use by dilution with water. To preclude these disadvantages of the concentrates it is necessary to add to the concentrates auxiliaries which are likewise subject to the restrictions described for the agents.        4. Many agents require the addition of appropriate auxiliaries for it to be possible to handle the agents in solutions diluted for use (and for example to afford solutions for use which are clear in the use concentration).        5. Many agents are effective only for certain micro-organisms. The formulation of disinfectants (solutions for use, concentrates) with three or more components in order to ensure efficacy for all relevant microbes leads to additional problems, however.        6. Many agents are unacceptable as residues even in small quantities, which is why careful rinsing of the disinfected surface with water is necessary. This procedure is uneconomic, time-consuming, of low environmental compatibility and may lead through the rinsing water to recontamination with unwanted microorganisms.        
The Patent DRP 649 206 of 5 Aug. 1937 relates to a disinfection method in which a glycerol monoalkyl ether is used as aqueous solution or emulsion, for example for disinfectant treatment of equipment in the food and other consumables industries. The glycerol monoalkyl ethers specifically disclosed are glycerol monododecyl ether, glycerol monodecyl ether, glycerol monooctyl ether, glycerol monobenzyl ether, diglycerol monooctyl ether, glycerol monocyclohexyl ether, and a mixture of glycerol monooctyl, monodecyl and monododecyl ethers. However, at room temperature, glycerol ethers without other agents have virtually no effect on microorganisms or have an effect only with long exposure times—but even then only inhibit microbial growth rather than actually kill microbes.
DRP 649 206 further states that dialkyl ethers of glycerol can be used with equal success. However, the only effect described is for selected glycerol ethers at 50° C. and on the yeast Mycoderma and the mould Oidium lactis (first table) and on thermobacteria, acetic bacteria, Penicillium, Oidium, Mycoderma and cultivated yeast (second table). The test methods are not disclosed. All the bacteria and fungi mentioned in the patent are important in the manufacture of food products where killing with a disinfectant is also occasionally necessary. They are not, however, pathogens and are therefore of no significance in hospitals or medical practices.
Following the teaching of DRP 649 206 and testing the activity of the glycerol ethers disclosed therein using present-day test methods reveals virtually no effect on microbes of hygienic relevance (such as the tubercle bacillus). An additional factor is that the compounds disclosed in DRP 649 206 are, for various practical reasons, useless for a modern (mechanical) thermochemical disinfection method.
For example, monooctyl glycerol ether is associated with the disadvantages that the ether when dissolved in water gives a solution which is always turbid and—which is particularly disadvantageous for modern mechanical thermochemical disinfection methods—highly foaming. DRP 615 171 of 6 Jun. 1935 in fact emphasizes the foam-stabilizing effect in this connection (cf. lines 56 et seq. therein). This has been confirmed for 1-(n-octyl)glycerol ether by the experiments carried out for the purposes of the present invention, which are detailed in the example section.
Dialkyl ethers of glycerol, e.g. dioctyl glycerol ethers, have no solubility in water and are unsuitable for the present object.
Accordingly, no compositions containing glycerol ethers for thermochemical disinfection are known to be on the market, and the monoalkyl glycerol ethers mentioned in DRP 649 206 are not available in commercial quantities. This can also be explained by hindsight and on the basis of the present invention by the facts that glycerol ethers display no microbicidal activity at room temperature in acceptable use concentrations, whereas the compositions conventionally used for thermochemical disinfection methods are effective even at room temperature, and the activity was merely improved by raising the temperature. Compositions displaying a very steep temperature gradient (starting from a low or absent activity at room temperature) are not generally known on the market.
DE-A-40 26 756 relates to preservatives which contain as synergistic agents a mixture of a) an organic acid, b) a monophenyl glycol ether and c) a guanidine derivative. Examples 13 and 14 are concentrates with more than 60% by weight of phenoxyethanol and respectively 15 and 10% by weight of glycerol monoalkyl ether. The preservatives in DE-40 26 756 are effective for various bacteria and yeasts. The applicant's post-published DE A-102 24 979 discloses mixtures of glycerol ethers with aromatic alcohols for controlling mycobacteria. Use of the mixtures at elevated temperature is not described.
DE-A-41 40 474 relates to the use of glycerol monoalkyl ethers as refatting skincare additives. DE-A-100 25 122, DE-A-100 25 123 and DE-A-100 25 124 disclose preparations having a content of glycerol monoalkyl ether. The preparations are used for preserving cosmetic and dermatological preparations. DE-C-42 40 674 discloses that glycerol monoalkyl ethers of the formula R—O—CH2—CHOH—CH2OH have a deodorant effect. DE-C-41 40 473 discloses compositions which can be used as skin antiseptics and hand disinfectants and which contain a combination of an aliphatic C1- to C6-alkyl alcohol component and at least one glycerol monoalkyl ether in aqueous solution, and further states that the use of glycerol monoalkyl ethers in preparations containing considerable quantities of water is entirely inadequate without further additions which likewise have antimicrobial activity.
DE-A-41 24 664 describes mixtures having antimicrobial activity and containing a synergistic combination of aryl-substituted alkanol with diol. Exemplary diols are glycerol monoalkyl ethers. The mixtures are used to preserve aqueous preparations of substances susceptible to microbial degradation (oils, fats, proteins, carbohydrates or derivatives thereof).
The present invention was thus based on the object of providing a composition for thermochemical disinfection of surfaces of articles such as instruments and thermolabile materials, which satisfies the stated requirements and avoids the disadvantages of the state of the art. The object was in particular to provide for a (mechanical) thermochemical disinfection method a composition which                does not attack or attacks negligibly materials used in the hospital sector as surfaces of articles and which must be disinfected, also above room temperature, and        has no irritant or defatting effect on contact with human skin (that is, does not necessarily have a high content of lower alcohols such as ethanol or isopropanol).        